This invention relates to brake systems for vehicles, and more particularly to brake boosters for such systems.
A typical brake system for a vehicle includes a device known as a brake booster, which is used to amplify the force applied directly to a brake pedal by an operator of the vehicle. The booster is typically mounted outside of the passenger compartment in the engine compartment on a firewall, dashboard, or panel forming the front wall of the passenger compartment. A push rod extends from the booster through an opening in the front panel for connection with a brake pedal assembly located within the passenger compartment. A flexible boot, or a sliding seal is provided around the push rod for environmentally sealing the hole in the front panel while allowing movement of the push rod by the brake pedal.
The booster is mounted in this fashion because it must draw in and expel a volume of air through a breather port surrounding the push rod, as the brake pedal is depressed and released. This drawing in and expulsion of air through the breather port unavoidably generates noise that would be objectionable to passengers in the vehicle, if the booster were mounted within the passenger compartment.
The shape of the booster generally requires that some sort of spacer be provided between the rear surface of the brake booster and the front panel of the passenger compartment. The interfaces between the spacer and both the front panel of the passenger compartment, and the rear surface of the booster must be sealed against leakage of air, and entry into the passenger compartment of noise, dirt, water, or other solid and liquid contaminants that are present in the engine compartment.
In order to support the weight of the booster when mounted in a cantilevered fashion spaced out from the panel, and to ensure that the interfaces between the spacer, panel and booster are sealed, boosters are typically secured to the panel by several threaded studs which extend trough the spacer and out the back of the spacer far enough to allow attachment of the booster and spacer to the panel. The spacer must therefore be strong enough to withstand the clamping force of tightening the bolts, and any other structural loads imposed during operation of the booster or vehicle. It is desirable that the spacer be light in weight, and be manufacturable at low cost, to improve fuel economy and reduce the price of the vehicle.
To improve sealing of the interfaces between the spacer, panel and booster, prior spacer arrangements typically required the use of a gasket on either end of the spacer. An adhesive foam gasket is often used. The need for using such gaskets adds unwanted cost and complexity to the spacer. The gaskets are also subject to damage and loss during shipment of the booster.
To facilitate installation, and to protect the alignment of the threaded studs, it is desirable that the spacer be installed on the threaded studs of the brake booster prior to shipping the booster. To ensure that the spacer stays in place during shipping and attachment of the booster to the panel of the passenger compartment, it is desirable that the spacer be retained in some manner on the threaded studs after the spacer is installed on the booster. It is desirable that retention of the spacer on the studs not require any additional parts of operations, such as shipping caps, or application and removal of tape.
What is needed, therefore, is an improved apparatus and method for mounting a brake booster using a spacer in a manner that provides a solution to one or more of the problems described above.
Our invention provides such an improved method and apparatus for mounting a brake booster on a panel through the use of a spacer having one or more integral flexible sealing lips for sealing the interfaces between the spacer, and either or both of the booster and the panel.
In one form of our invention, the spacer includes an integral flexible sealing lip adapted for sealing against either the booster or the panel of the passenger compartment. The spacer may also include a second integral flexible sealing lip adapted for sealing against either the booster or the panel of the passenger compartment, such that both the interface between the booster and the spacer and the interface between the spacer and the panel are sealed by the integral flexible sealing lips, thereby totally eliminating the need for additional gaskets required by prior spacer designs.
In another form of our invention, the spacer includes holes for passage therethrough of the threaded studs of the booster. The spacer may also include integral retaining tabs adapted to engage the threads on the threaded studs for holding the spacer in place during shipment of the booster and spacer, and during attachment of the booster and spacer to the front panel of the passenger compartment of the vehicle.
The spacer may be constructed of a lightweight material, such as a thermoplastic. The spacer may also include metal tubular inserts around the holes for resisting compressive loads on the spacer when installed between the booster and the panel, and for setting a desired deflection of the integral flexible sealing lips of the spacer
The foregoing and other features and advantages of the invention are apparent from the following detailed description of exemplary embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.